Synthesis of Previously Inaccessible Derivatives of 1,4,7‐Tri‐R‐1,4,7‐Triazacyclononane, Including Chiral Examples, and a Rapid Synthesis of the HCl Salts of H3tacn and H4dtne

Abstract

The synthesis of 1,4‐di‐tert‐butyl‐7‐R‐1,4,7‐triazacyclononane (tBu2Rtacn) derivatives through a “crab‐like” cyclization is reported. The tert‐butyl groups were cleavable with concentrated hydrochloric acid, allowing for a facile and convenient synthesis of the HCl salt of H3tacn and the most direct route to its industrially relevant binucleating N‐ethylene bridged derivative, H4dtne. In addition, the synthesis of chiral tacn derivatives with both one and two stereocenters in non‐annulet, alpha‐N positions is reported.